An internal-combustion engine is provided with a number of cylinders, each of which is connected to an intake manifold via at least one intake valve and to an exhaust manifold via at least one exhaust valve. The intake manifold receives fresh air (i.e., air coming form the outside environment) through a supply pipe provided with a throttle valve and is connected to the cylinders by means of respective intake pipes, each of which terminates in a position corresponding to at least one intake valve.
In a modern internal-combustion engine, the intake manifold can be of the variable-geometry type; i.e., it can be provided with a partialization device, which varies the cross section of the intake pipes as a function of the engine regime (i.e., the r.p.m. of the engine shaft). At low r.p.m. the section of passage of the air through the intake pipes is reduced so as to generate in the flow of intake air turbulences which improve mixing between air and fuel in the cylinders. Thanks to the presence of these turbulences which improve mixing, all the fuel injected is burnt and the pollutant emissions generated by combustion are thus reduced. At high r.p.m. the section of passage of the air through the intake pipes is maximized so as to enable a complete filling of the cylinders and hence generation of the maximum possible power.
For example, the partialization devices of the same type as the one described above may be either tumble devices or else swirl devices. A tumble device uses for each intake pipe a partialization body that is mobile away from and to an active position, in which the partialization body reduces the cross section of the intake pipe. A swirl system envisages that each intake pipe comprises two channels parallel to one another and set alongside one another and uses for each intake pipe a partialization body that is mobile away from and to an active position, in which the partialization body closes one of the two channels of the intake pipe completely.
In partialization devices present on the market, all the partialization bodies are fitted on a common shaft so as to rotate together away from and to the active position under the thrust of a common actuator device, which is designed to control in a simultaneous and synchronous way the position of all the partialization bodies themselves. In addition, in partialization devices present on the market, a position sensor is provided, which is generally coupled to the common actuator device or to the common shaft and determines the position of the partialization bodies, thus determining the angular position of the common shaft.
However, currently known position sensors used in partialization devices available on the market are costly and complex to install. In addition, since known position sensors detect the angular position of the common shaft, they do not detect directly the actual position of the partialization bodies and hence are not able to detect whether, on account of a mechanical problem, one of the partialization bodies no longer receives motion from the actuator device. Finally, on account of their dimensions, known position sensors are suitable for being coupled to the common shaft, but are not suitable for being coupled to a single partialization body to determine directly the actual position of the partialization body itself. In this connection, it should be noted that proper operation of a partialization device is necessary for reducing the pollutant emissions generated by combustion at low r.p.m. Consequently, an accurate control of proper operation of the partialization device is necessary to meet the requirements of the European-Community standard referred to as EURO-4.
WO2006045027A1 discloses a charge motion control valve actuator method and apparatus that utilizes a motor, an output shaft, a control circuit, and a sensor to provide closed loop control of the position of the output shaft via the motor; feedback from the sensor enables the control circuit to control the position of the output shaft, and the control circuit can also output data relating to the position of the output shaft.